J2EE Interview Questions and Answers 15

What is queue ?
A messaging system built on the concept of message queues. Each message is addressed to a specific queue; clients extract messages from the queues established to hold their messages.

What is RAR ?
Resource Adapter Archive. A JAR archive that contains a resource adapter module.

What is RDF ?
Resource Description Framework. A standard for defining the kind of data that an XML file contains. Such information can help ensure semantic integrity-for example-by helping to make sure that a date is treated as a date rather than simply as text.

What is RDF schema ?
A standard for specifying consistency rules that apply to the specifications contained in an RDF.

What is realm ?
See security policy domain. Also, a string, passed as part of an HTTP request during basic authentication, that defines a protection space. The protected resources on a server can be partitioned into a set of protection spaces, each with its own authentication scheme or authorization database or both. In the J2EE server authentication service, a realm is a complete database of roles, users, and groups that identify valid users of a Web application or a set of Web applications.

What is reentrant entity bean ?
An entity bean that can handle multiple simultaneous, interleaved, or nested invocations that will not interfere with each other.

What is reference ?
A reference to an entity that is substituted for the reference when the XML document is parsed. It can reference a predefined entity such as <>

What is registry ?
An infrastructure that enables the building, deployment, and discovery of Web services. It is a neutral third party that facilitates dynamic and loosely coupled business-to-business (B2B) interactions.

What is registry provider ?
An implementation of a business registry that conforms to a specification for XML registries (for example, ebXML or UDDI).

What is relationship field ?
A virtual field of an entity bean having container-managed persistence; it identifies a related entity bean.

What is remote interface ?
One of two interfaces for an enterprise bean. The remote interface defines the business methods callable by a client.

What is remove method ?
Method defined in the Home interface and invoked by a client to destroy an enterprise bean.

What is render kit ?
A set of renderers that render output to a particular client. The JavaServer Faces implementation provides a standard HTML render kit, which is composed of renderers that can render HMTL markup.

What is renderer ?
A Java class that can render the output for a set of JavaServer Faces UI components.

What is resource adapter ?
A system-level software driver that is used by an EJB container or an application client to connect to an enterprise information system. A resource adapter typically is specific to an enterprise information system. It is available as a library and is used within the address space of the server or client using it. A resource adapter plugs in to a container. The application components deployed on the container then use the client API (exposed by the adapter) or tool-generated high-level abstractions to access the underlying enterprise information system. The resource adapter and EJB container collaborate to provide the underlying mechanisms-transactions, security, and connection pooling-for connectivity to the enterprise information system.

J2EE Interview Questions and Answers 14

What is parameter entity ?
An entity that consists of DTD specifications, as distinct from a general entity. A parameter entity defined in the DTD can then be referenced at other points, thereby eliminating the need to recode the definition at each location it is used.

What is parsed entity ?
A general entity that contains XML and therefore is parsed when inserted into the XML document, as opposed to an unparsed entity.

What is parser ?
A module that reads in XML data from an input source and breaks it into chunks so that your program knows when it is working with a tag, an attribute, or element data. A nonvalidating parser ensures that the XML data is well formed but does not verify that it is valid. See also validating parser.

What is passivation ?
The process of transferring an enterprise bean from memory to secondary storage. See activation.

What is persistence ?
The protocol for transferring the state of an entity bean between its instance variables and an underlying database.

What is persistent field ?
A virtual field of an entity bean that has container-managed persistence; it is stored in a database.

What is POA ?
Portable Object Adapter. A CORBA standard for building server-side applications that are portable across heterogeneous ORBs.

What is point-to-point messaging system ?
A messaging system built on the concept of message queues. Each message is addressed to a specific queue; clients extract messages from the queues established to hold their messages.

What is primary key ?
An object that uniquely identifies an entity bean within a home.

What is principal ?
The identity assigned to a user as a result of authentication.

What is privilege ?
A security attribute that does not have the property of uniqueness and that can be shared by many principals.

What is processing instruction ?
Information contained in an XML structure that is intended to be interpreted by a specific application.

What is programmatic security ?
Security decisions that are made by security-aware applications. Programmatic security is useful when declarative security alone is not sufficient to express the security model of an application.

What is prolog ?
The part of an XML document that precedes the XML data. The prolog includes the declaration and an optional DTD.

What is public key certificate ?
Used in client-certificate authentication to enable the server, and optionally the client, to authenticate each other. The public key certificate is the digital equivalent of a passport. It is issued by a trusted organization, called a certificate authority, and provides identification for the bearer.

What is publish/subscribe messaging system ?
A messaging system in which clients address messages to a specific node in a content hierarchy, called a topic. Publishers and subscribers are generally anonymous and can dynamically publish or subscribe to the content hierarchy. The system takes care of distributing the messages arriving from a node's multiple publishers to its multiple subscribers.

What is query string ?
A component of an HTTP request URL that contains a set of parameters and values that affect the handling of the request.

J2EE Interview Questions and Answers 17

What is security attributes ?
A set of properties associated with a principal. Security attributes can be associated with a principal by an authentication protocol or by a J2EE product provider or both.

What is security constraint ?
A declarative way to annotate the intended protection of Web content. A security constraint consists of a Web resource collection, an authorization constraint, and a user data constraint.

What is security context ?
An object that encapsulates the shared state information regarding security between two entities.

What is security permission ?
A mechanism defined by J2SE, and used by the J2EE platform to express the programming restrictions imposed on application component developers.

What is security permission set ?
The minimum set of security permissions that a J2EE product provider must provide for the execution of each component type.

What is security policy domain ?
A scope over which security policies are defined and enforced by a security administrator. A security policy domain has a collection of users (or principals), uses a well-defined authentication protocol or protocols for authenticating users (or principals), and may have groups to simplify setting of security policies.

What is security role ?
An abstract logical grouping of users that is defined by the application assembler. When an application is deployed, the roles are mapped to security identities, such as principals or groups, in the operational environment. In the J2EE server authentication service, a role is an abstract name for permission to access a particular set of resources. A role can be compared to a key that can open a lock. Many people might have a copy of the key; the lock doesn't care who you are, only that you have the right key.

What is security technology domain ?
A scope over which the same security mechanism is used to enforce a security policy. Multiple security policy domains can exist within a single technology domain.

What is security view ?
The set of security roles defined by the application assembler.

What is server certificate ?
Used with the HTTPS protocol to authenticate Web applications. The certificate can be self-signed or approved by a certificate authority (CA). The HTTPS service of the Sun Java System Application Server Platform Edition 8 will not run unless a server certificate has been installed.

What is server principal ?
The OS principal that the server is executing as.

What is service element ?
A representation of the combination of one or more Connector components that share a single engine component for processing incoming requests.

What is service endpoint interface ?
A Java interface that declares the methods that a client can invoke on a Web service.

What is servlet ?
A Java program that extends the functionality of a Web server, generating dynamic content and interacting with Web applications using a request-response paradigm.

What is servlet container ?
A container that provides the network services over which requests and responses are sent, decodes requests, and formats responses. All servlet containers must support HTTP as a protocol for requests and responses but can also support additional request-response protocols, such as HTTPS.

What is servlet container, distributed ?
A servlet container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.

J2EE Interview Questions and Answers 16

What is resource adapter module ?
A deployable unit that contains all Java interfaces, classes, and native libraries, implementing a resource adapter along with the resource adapter deployment descriptor.

What is resource manager ?
Provides access to a set of shared resources. A resource manager participates in transactions that are externally controlled and coordinated by a transaction manager. A resource manager typically is in a different address space or on a different machine from the clients that access it. Note: An enterprise information system is referred to as a resource manager when it is mentioned in the context of resource and transaction management.

What is resource manager connection ?
An object that represents a session with a resource manager.

What is resource manager connection factory ?
An object used for creating a resource manager connection.

What is RMI ?
Remote Method Invocation. A technology that allows an object running in one Java virtual machine to invoke methods on an object running in a different Java virtual machine.

What is RMI-IIOP ?
A version of RMI implemented to use the CORBA IIOP protocol. RMI over IIOP provides interoperability with CORBA objects implemented in any language if all the remote interfaces are originally defined as RMI interfaces.

What is role (development) ?
The function performed by a party in the development and deployment phases of an application developed using J2EE technology. The roles are application component provider, application assembler, deployer, J2EE product provider, EJB container provider, EJB server provider, Web container provider, Web server provider, tool provider, and system administrator.

What is role mapping ?
The process of associating the groups or principals (or both), recognized by the container with security roles specified in the deployment descriptor. Security roles must be mapped by the deployer before a component is installed in the server.

What is role (security) ?
An abstract logical grouping of users that is defined by the application assembler. When an application is deployed, the roles are mapped to security identities, such as principals or groups, in the operational environment. In the J2EE server authentication service, a role is an abstract name for permission to access a particular set of resources. A role can be compared to a key that can open a lock. Many people might have a copy of the key; the lock doesn't care who you are, only that you have the right key.

What is rollback ?
The point in a transaction when all updates to any resources involved in the transaction are reversed.

What is root ?
The outermost element in an XML document. The element that contains all other elements.

What is SAX ?
Abbreviation of Simple API for XML.

What is Simple API for XML ?
An event-driven interface in which the parser invokes one of several methods supplied by the caller when a parsing event occurs. Events include recognizing an XML tag, finding an error, encountering a reference to an external entity, or processing a DTD specification.

What is schema ?
A database-inspired method for specifying constraints on XML documents using an XML-based language. Schemas address deficiencies in DTDs, such as the inability to put constraints on the kinds of data that can occur in a particular field. Because schemas are founded on XML, they are hierarchical. Thus it is easier to create an unambiguous specification, and it is possible to determine the scope over which a comment is meant to apply.

What is Secure Socket Layer (SSL) ?
A technology that allows Web browsers and Web servers to communicate over a secured connection.

J2EE Interview Questions and Answers 19

What is tool provider ?
An organization or software vendor that provides tools used for the development, packaging, and deployment of J2EE applications.

What is transaction attribute ?
A value specified in an enterprise bean's deployment descriptor that is used by the EJB container to control the transaction scope when the enterprise bean's methods are invoked. A transaction attribute can have the following values: Required, RequiresNew, Supports, NotSupported, Mandatory, or Never.

What is transaction ?
An atomic unit of work that modifies data. A transaction encloses one or more program statements, all of which either complete or roll back. Transactions enable multiple users to access the same data concurrently.

What is transaction isolation level ?
What is transaction isolation level The degree to which the intermediate state of the data being modified by a transaction is visible to other concurrent transactions and data being modified by other transactions is visible to it.

What is transaction manager ?
Provides the services and management functions required to support transaction demarcation, transactional resource management, synchronization, and transaction context propagation.

What is Unicode ?
A standard defined by the Unicode Consortium that uses a 16-bit code page that maps digits to characters in languages around the world. Because 16 bits covers 32,768 codes, Unicode is large enough to include all the world's languages, with the exception of ideographic languages that have a different character for every concept, such as Chinese.

What is Universal Description, Discovery and Integration (UDDI) project ?
An industry initiative to create a platform-independent, open framework for describing services, discovering businesses, and integrating business services using the Internet, as well as a registry. It is being developed by a vendor consortium.

What is Universal Standard Products and Services Classification (UNSPSC) ?
A schema that classifies and identifies commodities. It is used in sell-side and buy-side catalogs and as a standardized account code in analyzing expenditure.

What is unparsed entity ?
A general entity that contains something other than XML. By its nature, an unparsed entity contains binary data.

What is URI ?
Uniform resource identifier. A globally unique identifier for an abstract or physical resource. A URL is a kind of URI that specifies the retrieval protocol (http or https for Web applications) and physical location of a resource (host name and host-relative path). A URN is another type of URI.

What is URL ?
Uniform resource locator. A standard for writing a textual reference to an arbitrary piece of data in the World Wide Web. A URL looks like this: protocol://host/local info where protocol specifies a protocol for fetching the object (such as http or ftp), host specifies the Internet name of the targeted host, and local info is a string (often a file name) passed to the protocol handler on the remote host.

What is URL path ?
The part of a URL passed by an HTTP request to invoke a servlet. A URL path consists of the context path + servlet path + path info, where Context path is the path prefix associated with a servlet context of which the servlet is a part. If this context is the default context rooted at the base of the Web server's URL namespace, the path prefix will be an empty string. Otherwise, the path prefix starts with a / character but does not end with a / character. Servlet path is the path section that directly corresponds to the mapping that activated this request. This path starts with a / character. Path info is the part of the request path that is not part of the context path or the servlet path

What is URN ?
Uniform resource name. A unique identifier that identifies an entity but doesn't tell where it is located. A system can use a URN to look up an entity locally before trying to find it on the Web. It also allows the Web location to change, while still allowing the entity to be found.

What is user data constraint ?
Indicates how data between a client and a Web container should be protected. The protection can be the prevention of tampering with the data or prevention of eavesdropping on the data.

J2EE Interview Questions and Answers 18

What is servlet context ?
An object that contains a servlet's view of the Web application within which the servlet is running. Using the context, a servlet can log events, obtain URL references to resources, and set and store attributes that other servlets in the context can use.

What is servlet mapping ?
Defines an association between a URL pattern and a servlet. The mapping is used to map requests to servlets.

What is session ?
An object used by a servlet to track a user's interaction with a Web application across multiple HTTP requests.

What is session bean ?
An enterprise bean that is created by a client and that usually exists only for the duration of a single client-server session. A session bean performs operations, such as calculations or database access, for the client. Although a session bean can be transactional, it is not recoverable should a system crash occur. Session bean objects either can be stateless or can maintain conversational state across methods and transactions. If a session bean maintains state, then the EJB container manages this state if the object must be removed from memory. However, the session bean object itself must manage its own persistent data.

What is SGML ?
Standard Generalized Markup Language. The parent of both HTML and XML. Although HTML shares SGML's propensity for embedding presentation information in the markup, XML is a standard that allows information content to be totally separated from the mechanisms for rendering that content.

What is SOAP ?
Simple Object Access Protocol. A lightweight protocol intended for exchanging structured information in a decentralized, distributed environment. It defines, using XML technologies, an extensible messaging framework containing a message construct that can be exchanged over a variety of underlying protocols.

What is SOAP with Attachments API for Java (SAAJ) ?
The basic package for SOAP messaging, SAAJ contains the API for creating and populating a SOAP message.

What is SQL ?
Structured Query Language. The standardized relational database language for defining database objects and manipulating data.

What is SQL/J ?
A set of standards that includes specifications for embedding SQL statements in methods in the Java programming language and specifications for calling Java static methods as SQL stored procedures and user-defined functions. An SQL checker can detect errors in static SQL statements at program development time, rather than at execution time as with a JDBC driver.

What is SSL ?
Secure Socket Layer. A security protocol that provides privacy over the Internet. The protocol allows client-server applications to communicate in a way that cannot be eavesdropped upon or tampered with. Servers are always authenticated, and clients are optionally authenticated.

What is stateful session bean ?
A session bean with a conversational state.

What is stateless session bean ?
A session bean with no conversational state. All instances of a stateless session bean are identical.

What is system administrator ?
The person responsible for configuring and administering the enterprise's computers, networks, and software systems.

What is tag ?
In XML documents, a piece of text that describes a unit of data or an element. The tag is distinguishable as markup, as opposed to data, because it is surrounded by angle brackets (<>). To treat such markup syntax as data, you use an entity reference or a CDATA section.

What is template ?
A set of formatting instructions that apply to the nodes selected by an XPath expression.

J2EE Interview Questions and Answers 20

What is user (security) ?
An individual (or application program) identity that has been authenticated. A user can have a set of roles associated with that identity, which entitles the user to access all resources protected by those roles.

What is validating parser ?
A parser that ensures that an XML document is valid in addition to being well formed. See also parser.

What is value-binding expression ?
A JavaServer Faces EL expression that refers to a property of a backing bean. A component tag uses this expression to bind the associated component's value or the component instance to the bean property. If the component tag refers to the property via its value attribute, then the component's value is bound to the property. If the component tag refers to the property via its binding attribute then the component itself is bound to the property.

What is virtual host ?
Multiple hosts plus domain names mapped to a single IP address.

What is W3C ?
World Wide Web Consortium. The international body that governs Internet standards. Its Web site is http://www.w3.org/.

What is WAR file ?
Web application archive file. A JAR archive that contains a Web module.

What is warning ?
A SAX parser warning is generated when the document's DTD contains duplicate definitions and in similar situations that are not necessarily an error but which the document author might like to know about, because they could be. See also fatal error, error.

What is Web application ?
An application written for the Internet, including those built with Java technologies such as JavaServer Pages and servlets, as well as those built with non-Java technologies such as CGI and Perl.

What is Web application, distributable ?
A Web application that uses J2EE technology written so that it can be deployed in a Web container distributed across multiple Java virtual machines running on the same host or different hosts. The deployment descriptor for such an application uses the distributable element.

What is Web component ?
A component that provides services in response to requests; either a servlet or a JSP page.

What is Web container ?
A container that implements the Web component contract of the J2EE architecture. This contract specifies a runtime environment for Web components that includes security, concurrency, life-cycle management, transaction, deployment, and other services. A Web container provides the same services as a JSP container as well as a federated view of the J2EE platform APIs. A Web container is provided by a Web or J2EE server.

What is Web container, distributed ?
A Web container that can run a Web application that is tagged as distributable and that executes across multiple Java virtual machines running on the same host or on different hosts.

What is Web container provider ?
A vendor that supplies a Web container.

What is Web module ?
A deployable unit that consists of one or more Web components, other resources, and a Web application deployment descriptor contained in a hierarchy of directories and files in a standard Web application format.

What is Web resource ?
A static or dynamic object contained in a Web application that can be referenced by a URL.

What is Web resource collection ?
A list of URL patterns and HTTP methods that describe a set of Web resources to be protected.